.nav-header {
    position: fixed;
    left: 0;
    top: 0;
    height: 1rem;
    z-index: 1000;
    width: 100%;
    box-sizing: border-box;
    text-align: center;
    line-height: 1rem;
    background-color: #2a2a2a;
    color: #fff;
    font-size: .3rem;
    i {
      position: absolute;
      left: 0;
      line-height: 1rem;
    }
  }



  .d-flex{
    display: flex;
    .flex1{
      flex: 1;
    }
    .flex2{
      flex: 2;
    }
    .flex3{
      flex: 3;
    }
  }